Almost immediately upon the invention of laser technology there has been a long felt need for effective laser protection system (LPS). Exposure to laser light can cause significant and sometimes permanent damage to persons and property depending upon the type of laser, the length of exposure and the intensity of the laser. For example, the parts of the eye which are of most serious concern in laser exposure hazards to the eye are the cornea, lens, pupil/iris, and retina.
There are three major mechanisms by which living tissue can be damaged by laser light which are thermal, acoustic, and photochemical. Thermal effects are the major cause of eye tissue damage by lasers. Energy from the laser is absorbed by the eye tissue in the form of heat which often causes localized intensive heating of sensitive eye tissues. The amount of thermal damage varies depending on the thermal sensitivity of the type of eye tissue. The thermal effects of laser exposure can range from erythema to an actual burning of the eye tissue. The main factors affecting thermal damage to eye tissue are the amount of the eye tissue exposed, the wavelength of laser light, the energy of the laser beam, and the length of time that the tissue is irradiated by the laser.
Laser beams are also capable of causing a localized vaporization of eye tissue which in turn can create a mechanical shockwave that is in turn propagated through the remaining eye tissue. These shockwaves can cause significant tearing of eye tissues. Lastly, laser light can also cause significant changes to the chemistry of cells in the eye, which can result in changes to eye tissue that impair or even destroy the vision of the eye.
The wavelengths of laser light that are of particular concern in the development of LPS are the portion of the electromagnetic (EM) spectrum known as the optical portion of the spectrum, which consists of the infrared (IR) (780 nm–1 mm), ultraviolet (UV) (200–400 nm) and also the visible portions of the EM spectrum wavelengths (400–780 nm) between them.
Early developed lasers operated predominantly at only two wavelengths making the development of LPS relatively simple. For instance, U.S. Pat. No. 4,601,533, Laser Eye Protection Visor Using Multiple Holograms (Moss 1986) teaches LPS protection for the then known laser wavelengths by use of holographic fringes. In this prior art each of the holograms has a predetermined fringe spacing designed to reflect a given wavelength. The angle of peak diffraction efficiency of one of the holograms in this patent is designed to always coincide with the line of sight to the eye in question. This prior art utilization of two holograms to reflect radiation of a given wavelength produce a system providing sufficient angular bandwidth suitable for wide angular coverage which was sufficient for that time.
However, the number of wavelengths of lasers that are now being used either militarily or commercially is proliferating. It is a matter of public knowledge that tunable or frequency agile lasers are currently being developed, having there most significant threat in military uses, and for which there is no suitable LPS. The present state of the art LPSs are based on narrow band spectral line rejection filters at the threat laser wavelengths, attenuating incident laser energy at these wavelengths and thus preventing laser radiation from injuring or killing and/or destroying property.
More recent developments of LPS systems such as U.S. Pat. No. 5,116,113 (Chu, 1992) teach laser eye protective devices using metal ion-containing polymers. Other efforts at manufacturing effective LPSs that are commercially available existing art are a combination of optical thin film coating technologies and absorbing dyes that are designed to protect the user from lasers in the infrared and visible portions of the electromagnetic spectrum. Leading research engineers in the industry are currently working to improve the transmission characteristics of laser-absorbing dyes, to evaluate the reflective (dielectric stack, holographic mirrors, and rugate filters) and hybrid technologies, and enhance LPS scratch resistance polycarbonate hard-coating technologies. This technology deposits wavelength specific filters on spectacles, goggles, and visors to prevent non-visible laser energy from damaging eyes. The addition of advanced filters (either holographic or rugate) can block visible laser energy, while allowing other visible light to pass unimpeded.
The technical approach of the prior art LPSs used to protect against fixed frequency lasers cannot be applied to protection from the agile or variable laser or even to protection from a larger number of fixed frequency lasers currently in use. Prior to the disclosed invention the only known way to protect from multiple wavelengths of lasers is to stack or sandwich multiple layers of these advanced filters. As more band rejection filters are built into a sandwich, however, transmissivity of the LPS at other wavelengths decreases also, making it unusable at night and severely limiting its utility in the daytime. It is well known in the prior art that the level of attenuation provided by prior art LPSs at present laser wavelengths are generally only adequate against lower powered lasers which are increasingly being used as military weapons.
The United States Homeland Security Agency and related U.S. government agencies have been concerned that commercial, as well as military, aircraft are both a prime target for laser weapon useage, primarily to induce flash blindness. The penetration of laser light into the cockpit of an aircraft, or vehicle of any sort, can temporarily, and if powerful enough, permanently blind the pilot or operator. This could have disastrous results. Recent news accounts in the U.S. of laser penetration into the cockpits of commercial aircraft has intensified the need to have some manner of protection from these very serious threats.
Laser sensors are well known and commercially available. The use of these laser sensors as part of laser protection has been taught and involves the use of sensors as part of a laser protection program. The sensors in the prior art provide laser illumination sensing and analysis capability prior to the exposure of the person being warned. In theory the time gained can be used by the person to take reflexive protection measures and engage in laser illumination evasion, which most often meant putting on the proper wavelength(s) LPS. Insofar as laser light travels at the speed of light, it is easy to recognize the inadequacy of this system which requires first deciding which LPS device is needed and then physically having to put the device on.
A review of prior and current LPS technologies reveal that there are no acceptable prior art active laser protection systems that protect against all laser light in one device. Also, there are no automatic or active LPS devices known in the prior art. The prior art reveals that the known LPS technology uses passive systems that are inadequate for the rapidly evolving laser weapon industry. Because the prior art has been limited to the use of laser-absorbing dyes, reflective (dielectric stack, holographic mirrors, and rugate filters) and hybrid technologies, the inherent limitations of these systems make it difficult, if not impossible, to protect a user from all the possible laser wavelengths, or do so automatically.
Furthermore, there is no prior art LPS devices that utilize laser detection to both automatically adapt the laser blocking aspect of the device as well as automatically display critical data regarding the number, nature (i.e. wavelength) and direction of one or more intruding laser beams. These features coupled with real time holographic projection of the visible spectrum to replace the non-laser blocked light that happens to be blocked because it is the same wavelength as the blocked laser is another feature not found in the prior art.
While each of these prior art LPS devices fulfill their respective particular objectives and requirements, and are most likely quite functional for their intended purposes, it will be noticed that none of the prior art cited disclose an apparatus and/or method that is automatic, portable, rugged, and lightweight and that can provide laser protection from all wavelengths of laser light.
As such, there apparently still exists the need for a new and improved active laser protection system to maximize the benefits to the user and minimize the risks of injury from its use.
In this respect, the present invention disclosed herein substantially corrects these problems and fulfills the need for such a device.